My chicks are 5 weeks old. Ameracaunas and RIR's. We live near the coast, so our climate is very mild. Our lows are mid to upper 40s and highs between 60 and 70. They seem to be getting really crowded and I don't have any ideas for anything intermediate. I didn't expect to have this many (13). I got extras per the advice of others but haven't lost anyone.
13 of them, temps are a bit chilly, but can you run a heat lamp to the coop for a week or two as they get used to the coop? As long as it's not drafty, they can snuggle up near a heat lamp and be just fine. Time to acclimate them to outdoor temps.
Our temps are the same as yours, and I have been letting my 3 week olds out in the pen during the day, but before dusk, they are back inside and under a heat lamp.
This allows them to get some exercise, safe from the curious baby, it cuts down on the cleaning I have to do.